The long term goal of this proposal is to develop methods for efficient delivery and expression of transgenes into keratinocytes for possible treatment of human diseases by somatic gene-based therapies. Ex vivo gene therapy involves removal of the target cells from body, transduction in vitro with viral vector and subsequent transplantation of the modified autologous cells back to the patient. This method requires surgical grafting, is time consuming and costly. Direct gene transfer to keratinocytes in epidermis would circumvent these difficulties. The objective of this research proposal is to develop a method to transduce basal keratinocytes in situ with retroviral vectors and achieve persistant presence of transgene in epidermal keratinocytes. This will be achieved by 1)induction of hyperplasia in epidermis to allow replication of basal keratinocytes required for retroviral integration, 2)determination of accessibility of basal cells to viral transduction using adenoviruses as a marker, 3)generation of very titer pseudotype retroviral vectors, 4)introduction of retroviral vectors to basal cells and determining persistency of the transgene in epidermis.